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A longstanding goal in the 3D printing community is plastic recycling, both for failed prints and waste plastic from water bottles and other sources. Because FFF (Fused-Filament Fabrication) 3D printers use filament made from thermoplastic, we could theoretically make use of much of the plastic that would otherwise end up in a landfill. But in reality, recycling plastic into usable filament has proven to be very difficult for a variety of reasons. Petamentor2 is a new filament machine that works with PET bottles and that shows some promise.
Like many similar machines, Petamentor2 works in a simple way. The user loads up an old water bottle made of PET (a very common plastic) and cuts a small strip to start. They then feed that through a hot end that melts the plastic strip and extrudes round filament. Once a little bit of extruded filament comes out, the user attaches that to a spool that mounts onto a motorized hub. From then on, the motor will spin and pull the filament onto the spool. The idea is that people should end up with a spool of PET filament that they can then print like any other filament.
But there are problems with this idea, as there are with every machine of this type. The most obvious is that conventional PET (Polyethylene Terephthalate) is a poor 3D printing material. PETG is common, but that “G” (for “glycol”) is very important for improving the printability of PET. That said, regular PET is printable if you’re willing to deal with the headaches it presents.
The bigger issue is consistency. Most 3D printer models do not have any kind of closed-loop feedback and do not know how much plastic they are truly extruding. They only know how much filament they push into the hot end, which they calculate by the length of the filament fed by the extruder gear. But a length of filament is a three-dimensional cylinder, which means that the calculated volume comes from the length and the diameter. If that diameter changes or the filament isn’t perfectly round, the volume calculations will be wrong and the printer will extrude more or less plastic than it intends to. That results in poor print quality.
Reputable filament manufacturers put a lot of effort into building machines that can produce very consistent filament in order to avoid those print quality issues. When a manufacturer gets lazy and produces inconsistent filament, people notice and stop buying that brand. Unfortunately, most home filament machines lack the necessary mechanisms to ensure consistency and don’t have sensors to check the output quality.
Petamentor2 seems to get around that problem with a special adjustable blade. During extrusion, the user can move the blade to change the thickness of the strip that feeds into the hot end. That should let them fine tune the input strip until they get the perfect filament output.
Still, I’m skeptical. There isn’t anything else to ensure consistency. The extruded filament may not be perfectly cylindrical and the motorized spool could easily stretch the filament and affect diameter. The Petamentor2’s website doesn’t show example prints made with this filament, which isn’t a good sign. The Petamentor2's Facebook group does contain a few example print photos, but the quality is difficult to determine.
If you do want to take a gamble on the Petamentor2, it is an open source project and you can build your own machine. It is a low-cost build that doesn’t even require programming, thanks to the use of off-the-shelf controllers for the spool motor, blade adjustment, and hot end. If you do build a Petamentor2, be sure to let us know if it works well for you!
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